Lumpy idle NC30

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Stoozak
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Lumpy idle NC30

Post by Stoozak » Sat Jun 14, 2014 9:57 pm

(Dual post from the jetting sticky)

Alright so I removed carbs, added washers and placed the needles in the correct positions (they were backwards), drilled the 2.5mm hole, rejetted to 118/120, and turned idle screws out 2.25 turns.

The bike goes like a rocket and the flat spot is gone, but I have a lumpy idle.

Occasionally it will be so lumpy that the revs drop until it cuts out completely.

Any ideas?

Vfr400 lumpy idle: http://youtu.be/NHws1-fboZo

Icemaestro
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Re: Lumpy idle NC30

Post by Icemaestro » Sat Jun 14, 2014 11:04 pm

Mine does that sometimes, I feel like it depends on the bike temperature? I forgot to check the float heights, so was hoping it was that...like you I had mine balanced before rejetting

Neosophist
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Re: Lumpy idle NC30

Post by Neosophist » Sun Jun 15, 2014 11:49 am

Sometimes wrong if its cutting out.

Your vaccum pipe ok? it could be running out of fuel if the pipe is leaking.

After adjusting the carbs (dont forget vavle clearances) you need to balance the carbs with vaccm gagues.


It should idle super smooth all day long
xivlia wrote:i dont go fast on this bike so really do not need a rear brake.. /
vic-vtrvfr wrote:Ask xivlia for help, he's tackled just about every problem u could think of...

Stoozak
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Re: Lumpy idle NC30

Post by Stoozak » Sun Jun 15, 2014 5:30 pm

Ok balanced the carbs using the drill bit method and it's much much better. No more lumpy idle. It is a little slow returning to idle but it might be my imagination, I'll take a video tomorrow for some opinions.

Out of interest is it possible to get to the pilot screws with the carbs on?

Stoozak
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Re: Lumpy idle NC30

Post by Stoozak » Mon Jun 16, 2014 11:28 am

Right, this is her at warm at idle. Heaps better than before.

http://youtu.be/okjrTdG8fvI

Your opinions on the rev drop off rate?

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vfrman
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Re: Lumpy idle NC30

Post by vfrman » Mon Jun 16, 2014 3:07 pm

Yep. It sounds a little slow to me. I can't remember what causes this, so I don't want to send you on a goose chase. Is the throttle free and are the cables not tight (if that makes sense)?

Stoozak
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Re: Lumpy idle NC30

Post by Stoozak » Mon Jun 16, 2014 3:45 pm

They seem to be. Is there an easy way to lube the cables from the top?

Neosophist
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Re: Lumpy idle NC30

Post by Neosophist » Mon Jun 16, 2014 4:21 pm

Revs hanging around 2000 rpm before it reutns to idle is classic sign of "lean condition"

do you have an airleak anywhere, most common is carbs not sealing in the rubbers themselves or the rubbers being knackered.

Spray something flammable like brake cleaner / easy start aroudn the carb rubbers when backing off the throttle, if it returns to idle quicker then you have a leak somewhere.
xivlia wrote:i dont go fast on this bike so really do not need a rear brake.. /
vic-vtrvfr wrote:Ask xivlia for help, he's tackled just about every problem u could think of...

Stoozak
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Re: Lumpy idle NC30

Post by Stoozak » Mon Jun 16, 2014 4:47 pm

Okie dokie, I'll replace the rubbers just to be safe.

Is there anything else I should be looking for or setting while I have the carbs off?

Stoozak
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Re: Lumpy idle NC30

Post by Stoozak » Mon Jun 16, 2014 9:27 pm

Ok so i sprayed all the rubbers and didnt get much reaction.

I took the carbs off and did find that the vacuum take off for the fuel tap wasnt tightened enough.

Anyway, I tightened it up, greased the rubbers and did it all back up. I also adjusted the pilot screws out a quarter turn.

It seems to be better, but it might be in my head!

http://youtu.be/Ss4eHS9UQmA
Last edited by Stoozak on Tue Jun 17, 2014 7:33 am, edited 1 time in total.

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